Momentum of a proton in de Broglie wavelength

[Alb]

Homework Statement

In quantum mechanics the de Broglie wavelength of an object depends
on its momentum according to λ=h/p where h is Planck's constant.
Protons of charge e and mass m are accelerated from rest through a
potential V. What is their de Broglie wavelength?

A) $2h/\sqrt{}meV$
B) $h/\sqrt{}2meV$
C) h$\sqrt{}meV$
D) $h/eV$

Homework Equations

I don't know.

The Attempt at a Solution

I just don't know what I have to search for to solve it.
How can I express p with e and V?

 

[invertioN]

Hello there.
As you probably know p=mv. From conservation of energy u have mv^2/2 = eU, here you can solve for the velocity v. After that you can use it to end up with answer B)

 

[Alb]

Thanks.